System and method for heating dynamo-electric machines



Get. 17, 1933. 5 BROWN 1,930,994

SYSTEM AND METHOD FOR HEATING DYNAMO ELECTRIC MACHINES Filed Dec. 24,1929 2 Sheets-Sneet 1 3 /n1 /e/7/or fr/c Bro wn E. BROWN Oct. 17, 1933.

SYSTEM AND METHOD FOR HEATING DYNAMO ELECTRIC MACHINES Filed Dec. 24.1929 2 Sheets-Sheet 2 quick full-load application thereon.- Y

Patented Oct. 17, 1933 SYSTEM AND METHOD FOR HEATING DYNAMO-ELECTRICMACHINES Eric Brown, Baden, Switzerland; assignor to AktiengesellschaitBrown Boveri &,Cie., Baden, Switzerland,a joint-stock company ofSwitzere land:

Application December 24, 1929, Serial No.

, 416,307, and in Germany December 24, 1928 5 Claims. v(o1. 171-252)This invention relates to improvements in electriccurrent generatorsand, particularly, to means for maintaining large generatorsincon'clition for substantially instantaneous starting at full load.Large generators cannot be placed under full load immediately uponstarting for the reason that the several portions'of the generator heatup at different'ratesthereby causing; stresses and strains in thegenerator structure. The copper portions embedded in the iron of therotor heat up more quickly than the ironypartly because of theheat-insulating qualities of the coverings of the copper. Suchaction,especially when fre quently repeated, materially shortensthe lifeof the copper insulation. A furtherjdifierence in the heating efiect islikewise apparent when large generators are quickly started, in that thecircumference of the rotor reaches the full load operating temperaturebefore the core thereof has'been materially heated. Such difference intemperature-conditions; causes stresses in the materials and may evencause bending of the shaft, thereby giving risetodestruc'tivevibrations.

Itis, therefore, among the objects of'thepresent invention to providemeans for maintaining generators, and particularly large generators, insuch condition'as will permit quick-starting Another objector thepresent invention is to provide means for maintaining generators in suchheatedcondition as to permit full-load operation thereof substantiallyimmediately after starting.

- Another object of the invention is to provide means for preheating andautomatically maintaining generators at the proper temperature forfull-loadoperation immediately upon starting by the" use of portions ofthe generator structure itself'in combination with exterior heatsources. @bjects and advantages, other than thoseabove set forth, willbe apparent from the following de scription and the accompanyingdrawings, in 1. 9 3

Figure 1 shows a side elevation of one embodie ment of the/inventionusing a ,heat source 'external to the generatorjor maintaining thetemperatu l ereoi, L y

Iig} 2 shows a modified form of the invention,

haw Fig- 1 Fig. 3 is a modified embodiment of the inven-v tion in whichportic n s of the generator tobe hea e a e utili e s he t; s urmaddition tome'ansior supplying heat from external sources thereto, and

also in Side elevation, which similar to. that Fig. 4 illustrates onemanner of using portions of the generator as a supplemental heatsource,

Referring more particularly to the drawings by characters'ofreferencathe reference numeral 6 indicates a generator which is enclosedin a sub;

stantially gas-tight manneryand to which are connected supply conduits'7, 8 having a common portion and connecting with the generatoro at theends thereof. A discharge conduit 9 is connected with the generatorstructure at'substan tially the central portion thereof. The supplyconduits '7, 8 and the discharge conduit 9 are con;-

nected by means of a blower 11 driven by a suit-- able source of power,such as a motor 12, for the purpose of maintaining the heat-carryingmedium within the'supply conduits 7, 8, within the gen- 'erator' housingand within the discharge com; duit 9; in circulation. The gasescirculating'i through the generator and thevarious conduit connectionstherewith are heated by means of a.

heat-exchanger 13 or aheating resistance '1 ar ranged in the "commonportion of the supply con-' duits 7, 8. The heat-exchanger 13 may besupplied for heating purposes with steam or hot water;

or any suitable heat-carrying medium"-from-'a suitable'source. It will,of course, be understood thatboth oreither the heat-exchanger 13 or theheating resistance 14 may be connected to provi e;

forltransmission of heat'to the gasesci'rcula through the supplyconduits, the generator,"

and

the discharge conduit circuit under the ac'tibiifer the blower 11, asabove set forth.

If it is desired to provide means for manate cally maintainingthegenerator G at a 'p'rdetermined temperature, a branch pipe'16is'connected with the common portion of the supply; conduits '1, 8,;immediately behind thefhe'atexchanger '13 and the heating resistance'fi."The branch pipe 16 is connected witha blower 17*, operated by a'suitable source of powersuch "as asteam'turbine 18, for maintaining thegases within the generatorin constant circulatio nby discharging thesame through a discharge pipe 19 connecting with the discharge conduit9. A heat ing' resistance 21 is shown arranged within the discharge pipe19, and is connected-by means or a suitable switch 22 to a regulatingrheostat23.

The amount of the rheostatresistance connected into the heating circuitis determined by the operation ofta suitable-thermostatic element 24'within, the by-pass pipe 25 between'the branch pipe 16and thedischargepipe 19.

' Intcase' it is desired to utilize the exhaust steam from the turbine18 as the heating medium; a thermostatically-operated valve, indicatedat 26,

I of the generator 6 are connected with a suitable is connected with theexhaust line 27 from the turbine 18 and. the heating resistance 21 isreplaced by a heat-exchanger of any suitable character.

It will be seen that the above embodiment of the invention providesmeans for maintaining the gases circulated about the stator and rotor ofa generator in a preheated condition either by manual operation of theheat-exchanger 13 or the heating resistance 14,or by thermostaticoperation of the heating resistance 21 or a heatexchanger inserted inthe discharge line 19 in place thereof.

When the automatic apparatus is used for controlling the temperature,some of the air from the outlet side of the blower 11 takes the path tothe right through the branch pipe 16, through the blower 1'7, and thenceby way of the discharge pipe 19 to the heating resistance 21, whereuponit mingles with the air being discharged from the generator 6 and passeswith this air through the blower 11. The amount of air passing throughthis circuit, and the amount of heat imparted thereto by the resistance21,

.aresufficient to maintain the air, circulated through the generator, atthe required temperature. The air passing through the by-pass pipe 25subjects the thermostatic element 24 to substantially the temperature ofthe air as it is forced into the generator, and this element operates toefiect variation of the temperature of the vheating resistance 21inversely proportionally to variations in the air temperature at this Pint.

, Figure 2 shows a modification of the present invention in which agenerator 28, driven by a turbine 29, is heated to maintain thegenerator in such condition as to be available as a reserve machine forinstantaneous starting. In this em- ;bodiment, a heat-exchanger 31,supplied with a heating medium from a suitable source, is connected withthe generator 28 and with a blower 32 for the purpose of circulating aheat-carrying medium therethrough.

Connections are made with the pipe leading from the generator 28 to theinlet of the blower 32- for discharging part of the heat-carrying mediumthrough a second generator 33, also driven by turbine 29, for thepurpose of 'maintaining this generator also in the proper heatedcondition necessary for instantaneous full-load operation upon starting.Connections are so arrangedthat the heat-carrying medium is supplied tothe generator 33 at one or more points,

;and is abstracted therefrom at a different point by means of acirculating blower 34 connected between the inlet and outlet connectionsbetween the generator 33 and the circulatory system connected with thegenerator 28. This method of maintaining both generators in a heatedcondition is particularly valuable for use in centraloperated stations,or for ships which are provided with electrically operated powertransmission, inasmuch as the rotors of the generators are usuallyslowly rotated so that the same are maintained in a uniformly heatedcondition which permits the application of the full load thereonimmediately upon starting.

The arrangement shown in Fig. 3 is similar to that shown in Fig. 1, withthe exception that the windings of the rotor itself are utilized asheating resistances to aid in maintaining the temperature of thegenerator at the predetermined value. For this purpose,.the slip rings36 source of current such as a generator '37 driven by a suitable sourceof power, such as a turbine 38. The amount of current supplied to thewindings of the rotor is determined by means of a regulating resistance39 controlled, in dependence on the temperature of the gases circulatingwithin the generator housing, by means of a thermostatic element 41operating a system of levers 42 for the purpose of cutting resistanceinto or out of the circuit. For the purpose of facilitating theconnection of the windings of the rotor for use as heating resistances,the ends of the several phases 46 and 47 are brought out in such mannerthat they may be connected in series by means of switches 48.

It will be seen that the present invention provides means whereby agenerator may be maintained at substantially the operating temperaturefor the purpose of making it possible to bring the same to full-loadimmediately after starting. According to the present invention, thisresult is attained either by the use of external heat sources fortransmitting heat to gases circulated through the generator, or by acombination of such external heat sources with the use of the rotorwindings as heating resistances. It will likewise be seen that thetemperature of the generator may be regulated either manually or automatically in the case of either the use of an external heat source orthe combination of the external heat source with the rotor windings asheating resistances.

Although but a few embodiments of this invention have been illustratedand described, it will be understood that various other embodiments arepossible, and that various changes may be made without departing fromthe spirit of the invention or the scope of the appended claims. 7

The invention claimed is:

1. In a system for maintaining an electric current generator inimmediately operative condition, a supply conduit connected with thegenerator, a discharge conduit connected with the generator, means forcirculating a heat-carrying medium through said conduits, a source ofheat for heating the heat-carrying medium, and thermostatic means forcontrolling the amount of heattransmitted to the heat carrying mediumfrom said heat source.

2. In the art of operation of a dynamo electric machine, the method ofmaintaining the temperature throughout the machine structuresubstantially constant, during non-operation thereof, at substantiallythe temperature developed during normal operation; said methodcomprising supplying a heat-carrying medium to the machine structure,and increasing the temperature of said medium when the temperaturethroughout the machine structure decreases from substantially thetemperature developed during normal operation of the machine.

3. In a system of the character described, a dynamo electric machine,means for supplying a heat-carrying medium to said machine comprising aclosed circuit including the machine, means operable independently ofsaid machine for causing said medium to circulate around said circuit,means operable independently of. the condition of operation of saidmachine for imparting heat to said medium, and means for controllingsaid medium-heating means responsive to variations in the temperature ofsaid medium, at a given point in said circuit, from a predetermineddegree of temperature.

4. In a system of the character described, a heat-carrying medium tosaid machine comprisdynamo electric machine, means for supplying a ing aclosed circuit including the machine, means heat-carrying medium to saidmachine comprisoperable independently of said machine for causing aclosed circuit including the machine, means ing said medium to circulatearound said circuit,

5 operable independently of said machine for causand means comprising anelectrical resistor and ing Said medium to circulate around Said C cuoperable independently of the condition of operaand means comprising anelectrical resistor and tion of said machine for imparting heat to saidOperable independently the conditifln 0f opermedium, said resistor beingembodied in said ation of said machine for imparting heat to saidmachine and forming at least part of the operat- 10 medium. ing windingsthereof. 5. In a system of the character described, a ERIC BROWN. dynamoelectric machine, means for supplying a 20 J I V Y Y I v v r i I V i sop g I I V v v as V i v t a I g I i v I a g I 40 g V Q i V g p v i i I 45I v 1 i I 7' I e co g p i a g I Y i g I v I a i r a 7 1 25 1 55 I I g pi I v V so l l V v I p g I v c5 7 V i g a g g 7 v 3 i I v p I 14c 70 g jI I g g I I a I 75 V A i i c a 15o

